Workplace stress levels are rising as many bosses refuse to replace workers who leave, expecting existing staff to lift their workloads instead.

A survey of 1392 Kiwi bosses and 1328 staff by recruitment company Hudson found that just 21.1 per cent of employers say they always replace employees when they leave, while 67.2 per cent have a sinking lid policy and spread the work among remaining workers.

As a result, 77 per cent of staff in the survey had taken on new or greater responsibilities and 41.6 per cent said they were more stressed than a year ago, with 56.4 per cent looking for a new job.

The survey results, contained in the Hudson Salary and Employment Insights 2013 report, also showed that the desire for higher pay was the biggest motivator to change jobs.

It found that 70.9 per cent of employers were planning pay rises in the 2-3 per cent range this year, motivated mainly by the need to retain top performers. Nearly 60 per cent of the bosses who were not planning to offer pay rises were worried about losing those key staff.

Hudson said more workers were shouldering extra responsibility and working longer hours and consequently wanted greater rewards.

The challenge for employers was to formally recognise and reward staff for commitment, loyalty and increased workload, while balancing their books, the report said.

"Where roles aren't being replaced, that's putting pressure on the current team and is not sustainable in the longer term," Hudson executive general manager Roman Rogers said. "Consequently, employers need to protect their position and steps to retain high performers, as high staff churn is counter-productive..

"With employees motivated by pay and budgets remaining tight, employers should prioritise spending and ensure rewards and benefits incentivise and retain high performers."

Surprisingly, the survey also found staff-morale levels were quite high, despite the increased workloads and lack of extra pay. This could be partly because employers had become better at communicating their plans and strategies to their staff during difficult times, the report said.

And while the amount in the pay packet was clearly extremely important to staff, other factors also played a role in morale.

"We know that strong staff engagement is needed for staff retention, so where budgets are tight, meaningful reward and recognition programmes can play a significant role in the salary package, with flexible working hours, bonuses and subsidised health benefits being the top three benefits offered by employers," Rogers said.